WASHINGTON (Reuters) - It may be possible to remove salt
from more water to boost the U.S. fresh water supply, but
additional studies need to be done to assess the environmental
effects of doing so, a panel said on Wednesday.

U.S. capacity to desalinate water grew by around 40 percent
between 2000 and 2005, and plants now exist in every state, the
National Research Council panel reported.

Most use reverse osmosis, which pushes water through a
membrane to separate out most salts. But it is expensive, uses
a great deal of energy and its effects on the environment are
unclear, the panel of engineers and other experts found.

The Earth is covered in water, but more than 97 percent of
it is seawater or brackish groundwater and cannot be drunk or
used for irrigation.

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"Uncertainties about desalination's environmental impacts
are currently a significant barrier to its wider use, and
research on these effects -- and ways to lessen them -- should
be the top priority," said Amy Zander, an engineering professor
at Clarkson University in Potsdam, New York, who chaired the
panel.

"Finding ways to lower costs should also be an objective. A
coordinated research effort dedicated to these goals could make
desalination a more practical option for some communities
facing water shortages," she said in a statement.

Seawater reverse osmosis, which uses membranes to filter
out the salt, uses about 10 times more energy than traditional
treatment of surface water, according to the report.

It may be possible to make the process more
energy-efficient by making the membranes more permeable, the
committee said. A method called thermal desalination is another
possibility.

The independent, advisory National Research Council, part
of the National Academies of Science, was asked to look into
the matter by the U.S. Environmental Protection Agency and the
U.S. Bureau of Reclamation.

Desalination may be less environmentally harmful than many
other ways to supplement water -- such as diverting freshwater
from sensitive ecosystems, the report said.

But researchers should find out whether fish and other
creatures get trapped in saltwater intake systems and what the
effects are of disposing of the salt concentrate created by
desalination, it said.

The report recommended that federal research and
development on desalination be overseen by the White House
Office of Science and Technology Policy and funded at current
levels of about $25 million a year.

Federal research on desalination lacks an overall strategic
direction, and the majority of research was left to the private
sector, it said.